Prompt injection in anhydrous ammonia agricultural storage and handling AI

Four adversarial injection surfaces in anhydrous ammonia agricultural AI

1. Bulk NH3 storage tank pressure AI (Emerson DeltaV NH3 terminal pressure AI / Yokogawa OpreX NH3 agricultural storage AI / Honeywell Experion PKS NH3 tank AI — continuous tank vapor-space pressure monitoring fed into AI trend classification)

Anhydrous ammonia is stored as a liquefied compressed gas in ASME-coded pressure vessels at fertilizer distribution terminals and on-farm bulk tanks ranging from 1,000 to 30,000 US gallons. The vapor-space pressure directly reflects the saturation pressure of liquid NH3 at the prevailing temperature — at 80°F (26.7°C) the saturation pressure is approximately 134 psig; at 85°F (29.4°C) it rises to approximately 148 psig; at 90°F (32.2°C) to approximately 163 psig. IIAR Bulletin 109 and CGA G-2.1-2014 require a minimum 10% vapor headspace at the reference filling temperature so that liquid thermal expansion during summer ambient temperature swings does not produce hydraulic overpressure. AI monitoring systems on Emerson DeltaV NH3 terminal platforms and Yokogawa OpreX NH3 storage controllers use screenshot images from the HMI pressure gauge panel, parsed by computer vision classifiers trained to distinguish normal saturation pressure trends from anomalous over-pressure transients and PRV approach events — typically alerting the control room when pressure exceeds a setpoint consistent with 90°F saturation and trending upward faster than seasonal ambient warming would explain.

In the adversarial scenario, the actual bulk tank vapor-space pressure gauge reads 155 psig, which at an ambient temperature of 85°F indicates liquid overfill reducing the vapor headspace below the 10% IIAR minimum — thermal expansion of the liquid NH3 at that fill level produces a pressure above the 148 psig saturation point for 85°F, indicating residual compression of the remaining vapor headspace. A ±10 DN downward pixel-shift attack on the HMI screenshot fed to the pressure AI suppresses this reading to a displayed 118 psig — consistent with the expected saturation pressure for a normal 80°F ambient condition with adequate headspace — so the AI classifier returns a status of "normal operating range, no alarm." The consequence chain is direct: the displayed 118 psig triggers no PRV approach warning; delivery tanker filling may continue or resume; as afternoon ambient temperatures climb from 85°F toward 95°F, the liquid volume expands further with no vapor headspace to absorb it; the pressure relief valve (PRV) lifts at its setpoint — typically 250 psig for ASME NH3 vessels — releasing NH3 vapor to the atmosphere at a rate that can exceed OSHA PSM reportable quantity thresholds within minutes. No OSHA PSM alarm, no EPA RMP notification, and no automated depressurization procedure is initiated, because the AI-monitored pressure displayed 118 psig throughout.

2. NH3 transfer hose gas detector AI (Honeywell XNX Universal Transmitter NH3 detector AI / Dräger X-am 5600 NH3 AI / MSA Ultima XIR NH3 AI — area gas detection during nurse tank fill operations at the distribution terminal transfer rack)

Transfer operations at anhydrous ammonia distribution terminals involve connecting nurse tanks — typically 1,000–1,500 US gallon applicator tanks — to the bulk storage terminal via flexible hose assemblies rated to ANSI/IIAR 2 and CGA G-2.1 hose standards. Electrochemical and catalytic-bead NH3 area gas detectors positioned at the transfer rack — feeding AI platforms from Honeywell Analytics, MSA Safety, and Dräger — continuously classify the ambient NH3 concentration from gas sensor readout images to determine whether hose integrity is being maintained during fill operations. OSHA 29 CFR 1910.111 and IIAR 2-2021 require that all NH3 transfer operations use excess-flow valves and appropriate hose assembly inspection, and that the transfer area be monitored for NH3 leak detection. The ACGIH TLV-TWA of 25 ppm and OSHA PEL of 50 ppm represent long-term occupational exposure limits; the NIOSH IDLH of 300 ppm represents the concentration above which a 30-minute exposure can cause irreversible injury or death; at 680 ppm the concentration is 2.3× IDLH — acute laryngospasm, chemical burns to the upper respiratory tract, and rapid loss of consciousness are all plausible outcomes within minutes.

The adversarial scenario involves a ±8 DN downward pixel-shift attack on the gas detector readout image fed to the NH3 area monitoring AI during a nurse tank fill event. The actual sensor reading is 680 ppm — arising from a partial hose coupling failure where the cam-lock fitting did not seat completely, producing a continuous NH3 jet leak at the connection point. The 680 ppm reading is suppressed to a displayed 18 ppm — below the OSHA PEL 50 ppm and roughly consistent with trace background NH3 from nearby soil injection equipment — so the AI gas detection system returns a "within acceptable limits" classification and raises no alert. Transfer personnel remain in the area; an operator approaching the coupling from downwind is exposed at 680 ppm for several minutes before experiencing eye and throat irritation severe enough to prompt voluntary retreat. No automatic excess-flow valve closure is triggered (the excess-flow valve responds to liquid flow rate anomalies, not vapor leak concentrations at the coupling); no evacuation, no emergency notification to the OSHA PSM emergency action plan coordinator. The OSHA PSM NH3 TQ of 10,000 lbs means this facility carries formal process safety requirements, but the AI gas monitoring layer — a supplement to the fixed detector hardwired alarming system — has been completely disabled by the pixel manipulation.

3. Nurse tank (field applicator) pressure AI (Case IH AFS Connect NH3 applicator AI / AGCO Fieldstar 5 NH3 application monitor AI / John Deere Operations Center NH3 AI — field nurse tank condition monitoring integrated with precision agriculture platforms)

Nurse tanks are highway-portable, nurse-towed agricultural NH3 applicators typically rated to 265 psig ASME working pressure, painted reflective white to reduce solar heat gain per IIAR and state agricultural department guidance. During peak planting and harvest seasons, nurse tanks may sit in full sun for 8–12 hours between refills, exposed to ambient temperatures that can exceed 100°F in Midwestern states. Case IH AFS Connect, AGCO Fieldstar 5, and John Deere Operations Center NH3 monitoring modules use AI-assisted image analysis of the nurse tank's analog pressure gauge — often photographed via cab-mounted camera or relayed from a Bluetooth pressure transmitter display — to classify tank condition as safe for continued field use, requiring inspection, or requiring return to the terminal. The saturation pressure of liquid NH3 at 80°F is approximately 134 psig; at 90°F it rises to approximately 163 psig; at 95°F ambient with a black-paint peeled dome exposed to direct solar radiation, effective surface temperatures can produce internal liquid temperatures approaching 105°F and saturation pressures approaching 195–200 psig — well below the 265 psig design working pressure but approaching the PRV setpoint which is typically set at 85% of design, approximately 225 psig.

In the adversarial attack, the actual nurse tank analog pressure gauge reads 198 psig — corresponding to elevated liquid temperature after reflective white paint has peeled from the top dome of the tank during a prior season, dramatically increasing solar heat absorption. A ±10 DN downward pixel-shift on the gauge image fed to the Case IH AFS Connect NH3 AI or John Deere Operations Center classifier suppresses the displayed reading to 142 psig, which is consistent with normal NH3 saturation at approximately 80°F ambient — a plausible reading for a partially shaded or early-morning condition. The AI returns a "normal operating pressure — continue field application" status; the operator has no independent means of verifying tank pressure from the cab and relies entirely on the connected monitoring display. As ambient temperatures continue to climb through afternoon, actual tank pressure approaches the 225 psig PRV setpoint; the PRV lifts, releasing an NH3 cloud at ground level near the operator cab in an open field — far from the distribution terminal's emergency response resources. OSHA 29 CFR 1910.111 governs anhydrous ammonia in agriculture and carries partial PSM exemptions, meaning some smaller operations may lack the formal Process Hazard Analysis and emergency action plan required of full PSM-covered facilities — a regulatory gap that makes AI monitoring integrity even more consequential.

4. Bulk storage tank level AI (Emerson DeltaV NH3 terminal level AI / Honeywell Experion PKS NH3 overfill monitor AI / Endress+Hauser Micropilot FMR NH3 tank level AI — radar or float-based fill level monitoring with AI overfill detection)

Bulk anhydrous ammonia storage terminals use radar level transmitters (Emerson Rosemount 5900S, Endress+Hauser Micropilot FMR series) or float-and-tape mechanical gauges to determine the liquid volume in the vessel, expressed as a percentage of total tank capacity. IIAR CGA G-2.1-2014 mandates a maximum liquid fill of 85% of tank volume at the reference filling temperature, providing the thermal expansion headspace required as ambient temperatures rise through the day and season. AI monitoring systems on Emerson DeltaV and Honeywell Experion PKS platforms parse HMI tank level gauge images to classify fill status against this 85% threshold, alert when a delivery tanker is filling the tank beyond safe limits, and generate automated stop-fill signals to the tank inlet valve controller. These systems are particularly important during night or weekend deliveries when the on-site PSM coordinator may not be physically present; the AI classification becomes the primary real-time overfill protection layer supplementing the hardwired high-level shutoff.

The adversarial attack uses a ±10 DN downward pixel-shift on the tank level gauge image to show a displayed fill of 74% while the actual fill level is 91% — 6 percentage points above the IIAR CGA G-2.1 maximum of 85%. At 91% fill with no vapor headspace adequate for thermal expansion, the bulk tank is in a thermally constrained condition: any rise in ambient temperature will be converted entirely into pressure rise rather than vapor-space compression. At a displayed 74%, the AI monitoring system classifies the tank as having ample headspace and raises no overfill alarm; the delivery tanker driver, relying on the terminal's AI-reported fill status, continues pumping. Combined with the Surface 1 scenario — where the actual vapor-space pressure is already 155 psig — the terminal is simultaneously overfilled and thermally over-pressured with no AI-generated alarm on either channel. The consequence is a compounding failure: as afternoon temperatures rise, the actual pressure advances toward the PRV setpoint; the PRV lifts; NH3 vapor is released at quantities that can reach EPA RMP worst-case toxic endpoint distances of several miles in Pasquill–Gifford F stability conditions. Glyphward pre-scans all four NH3 agricultural monitoring contexts before AI inference output is logged to the SCADA historian — try the free scanner to test your pipeline's resilience to these attacks.

Integration: anhydrous ammonia agricultural AI with Glyphward pre-scan gate

Glyphward integrates as a pre-scan gate between the HMI screenshot capture layer (or camera frame from precision agriculture cab displays) and the AI inference pipeline. Each image is submitted to the Glyphward API before the NH3 monitoring AI receives it; if the adversarial score meets or exceeds threshold 35 — chosen to reflect the OSHA PSM TQ of 10,000 lbs for NH3, the EPA RMP toxic TQ of 10,000 lbs, the IDLH of 300 ppm, the 15 fatalities at West Fertilizer in 2013, and the community-scale consequences of agricultural NH3 releases in open terrain adjacent to populated areas — the scan raises AdversarialNH3AgricultureImageError and the monitoring AI does not process the frame. The four contexts (TANK_PRESSURE, TRANSFER_HOSE_GAS_DETECTOR, NURSE_TANK_PRESSURE, TANK_LEVEL) correspond to the four adversarial surfaces described above. The unit_id ties each scan to a specific vessel or detector in the facility asset register for audit trail purposes required under OSHA PSM management of change and pre-startup safety review documentation.

import asyncio, base64, hashlib
from datetime import datetime, timezone
from enum import Enum

import httpx

GLYPHWARD_API_KEY = "YOUR_GLYPHWARD_API_KEY"
GLYPHWARD_SCAN_URL = "https://glyphward.com/v1/scan"

# Anhydrous ammonia agricultural AI contexts: threshold 35
# OSHA PSM 29 CFR 1910.119 NH3 TQ 10,000 lbs
# EPA RMP 40 CFR Part 68 NH3 toxic TQ 10,000 lbs
# OSHA 29 CFR 1910.111 anhydrous ammonia in agriculture (partial PSM exemption)
# IIAR Bulletin 109 / CGA G-2.1-2014 max fill 85%; min 10% vapor headspace
# ACGIH TLV-TWA 25 ppm; OSHA PEL 50 ppm; IDLH 300 ppm
# West Fertilizer Co., West TX, 17 Apr 2013: 15 killed, 160+ injured
NH3_AGRICULTURE_THRESHOLD = 35


class AnhydrousAmmoniaAgricultureContext(Enum):
    TANK_PRESSURE = "tank_pressure"
    TRANSFER_HOSE_GAS_DETECTOR = "transfer_hose_gas_detector"
    NURSE_TANK_PRESSURE = "nurse_tank_pressure"
    TANK_LEVEL = "tank_level"


class AdversarialNH3AgricultureImageError(Exception):
    """Raised when any NH3 agricultural monitoring image scores >= 35.
    TANK_PRESSURE uncaught: overfill thermal-pressure rise not alarmed, PRV lift.
    TRANSFER_HOSE_GAS_DETECTOR uncaught: 680 ppm (2.3x IDLH) shown as 18 ppm.
    NURSE_TANK_PRESSURE uncaught: solar heat gain at 198 psig shown as 142 psig.
    TANK_LEVEL uncaught: 91% fill (above 85% IIAR max) shown as 74%, filling continues."""

    def __init__(self, scan_id, score, context, unit_id, flagged_region=None):
        self.scan_id = scan_id
        self.score = score
        self.context = context
        self.unit_id = unit_id
        self.flagged_region = flagged_region
        super().__init__(
            f"Adversarial NH3 agriculture image: context={context.value} "
            f"score={score} unit={unit_id} scan_id={scan_id}"
        )


async def scan_nh3_agriculture_image(image_bytes, context, unit_id, client):
    image_hash = hashlib.sha256(image_bytes).hexdigest()
    payload = {
        "image": base64.b64encode(image_bytes).decode(),
        "source": f"nh3_agriculture:{context.value}:{unit_id}",
        "metadata": {
            "unit_id": unit_id,
            "context": context.value,
            "image_sha256": image_hash,
            "scan_timestamp_utc": datetime.now(timezone.utc).isoformat(),
        },
    }
    resp = await client.post(
        GLYPHWARD_SCAN_URL,
        headers={"Authorization": f"Bearer {GLYPHWARD_API_KEY}"},
        json=payload,
        timeout=4.0,
    )
    resp.raise_for_status()
    result = resp.json()
    if result.get("score", 0) >= NH3_AGRICULTURE_THRESHOLD:
        raise AdversarialNH3AgricultureImageError(
            scan_id=result["scan_id"],
            score=result["score"],
            context=context,
            unit_id=unit_id,
            flagged_region=result.get("flagged_region"),
        )
    return result


async def main():
    async with httpx.AsyncClient() as client:
        with open("nh3_agriculture_screenshot.png", "rb") as f:
            image_bytes = f.read()
        result = await scan_nh3_agriculture_image(
            image_bytes,
            AnhydrousAmmoniaAgricultureContext.TANK_PRESSURE,
            unit_id="NH3-TANK-WEST-1",
            client=client,
        )
        print(f"Clean scan: {result['scan_id']} score={result['score']}")


asyncio.run(main())

Frequently asked questions

What happened at West Fertilizer Company in West, Texas, in 2013?

On 17 April 2013, a fire triggered a catastrophic ammonium nitrate explosion at the West Fertilizer Company terminal in West, Texas, killing 15 people — 12 first responders — injuring 160+, and destroying 150+ buildings within a mile. OSHA cited the facility for multiple PSM violations under CSB Case 2013-02-I-TX. The facility stored anhydrous ammonia above the 10,000 lb PSM threshold, and the incident remains one of the deadliest US industrial accidents in recent decades.

What is the OSHA PSM threshold for anhydrous ammonia, and does it apply to agricultural storage?

The OSHA PSM TQ for NH3 is 10,000 lbs. Agricultural retail facilities selling NH3 directly to farmers may qualify for a partial exemption under OSHA 29 CFR 1910.111, but EPA RMP (40 CFR Part 68) applies an identical 10,000 lb toxic TQ with no agricultural exemption — creating a regulatory gap where an agricultural terminal may face EPA RMP requirements but only partial OSHA PSM obligations.

Why does an upward-direction (overfill) NH3 tank display attack use a downward pixel shift?

Because the physical overpressure condition is too high, suppressing it requires shifting the gauge needle image downward — a ±10 DN downward pixel shift moves the displayed reading from 155 psig to 118 psig, making the AI classify the dangerous over-pressure as a normal ambient-saturation reading. The attack direction (pixel shift direction) is always opposite to the direction of the hazardous physical deviation.

What is the IDLH for anhydrous ammonia and why does the 680 ppm Surface 2 scenario not trigger immediate fatality?

The NIOSH IDLH for NH3 is 300 ppm. At 680 ppm (2.3× IDLH), acute effects are severe respiratory irritation and laryngospasm rather than immediate incapacitation because NH3's strong odor provides some warning and its acute toxicity acts over minutes. Life-threatening pulmonary injury is the outcome of sustained unprotected exposure at 680 ppm, but unlike nerve agents or phosgene, there is a brief window for escape — a window eliminated when the gas detection AI shows 18 ppm and no alarm is raised.

Why is threshold 35 for anhydrous ammonia agricultural storage AI?

Threshold 35 reflects the OSHA PSM and EPA RMP TQ of 10,000 lbs, the IDLH of 300 ppm, the community-scale consequence demonstrated at West Fertilizer (15 killed, 160+ injured), the partial PSM agricultural exemption regulatory gap, and the compound four-surface attack geometry that mirrors multi-system failure sequences leading to catastrophic NH3 release at distribution terminals adjacent to residential areas.